PFC converters. One example is a method of operating a power converter, the method comprising: charging a first-phase inductance of a first boost converter, and then discharging the first-phase inductance, the charging and discharging defines a first switching period of the first boost converter; asserting, during the first switching period, a sync-two signal based on a duration of a prior switching period of the first boost converter and an offset value; asserting, during the first switching period, a valley-two signal when current through a second-phase inductance of a second boost converter reaches a predetermined valley current; responsive to the assertion of the sync-two signal and the valley-two signal, charging the second-phase inductance, and then discharging the second-phase inductance; and responsive to relative timing of the assertion of the sync-two signal and assertion of the valley-two signal, modifying the offset value.